The reciprocating internal combustion engine has undergone many evolutionary changes in the century it has been in existance. One of the aspects of the internal combustion engine which has remained most constant is the popularity of the carburetor for providing the air-fuel mixture to the engine.
The carburetor is inherently a steady-state device, and as such it can be finely tuned for a narrow range of operation. Within this narrow range, it performs optimally and it provides the correct air-fuel mixture. However, when the engine operating range is altered at all in engine speed, temperature, load, or the like, the carburetor becomes a very inefficient device for providing the correct air-fuel mixture for the conditions experienced by the engine.
These inherent defects in the carburetor have been recognized for years by those individuals skilled in the automotive arts. However, cheap fuel prices and a lack of concern for air quality in urban areas mitigated against any severe design changes in the carburetor.
In recent years, fuel prices have increased extraordinarily, and the degradation of air quality due to automotive exhaust emissions has become of vital concern. It has been found that when a carburetor is not operating within its narrow optimum range, it generally provides too much fuel to the internal combustion engine. When this occurs, the engine efficiency is reduced, the exhaust emissions of carbon monoxide, unburned hydrocarbons, and oxides of nitrogen, are increased. These exhaust compounds are the major contributors to the formation of smog in urban areas. The prior art includes recent patents which attempt to improve the performance of the standard carburetor. These patents, which reflect the state of the art, are the following: U.S. Pat. Nos. 3,868,933; 3,866,588; 3,738,109; 3,688,752; 3,599,426; and 3,533,386.
These patents generally relate to devices for introducing uncarbureted air into the intake manifold of the engine to improve the air-fuel ratio of the carbureted air during particular engine operating conditions. These conditions are sensed by manifold vacuum sensors, engine temperature sensors, and the like. The major drawback of these devices is that they do not respond correctly to the various combinations of engine operating parameters.